Altered platelet protein kinase C activity in bipolar affective disorder, manic episode.

Protein kinase C (PKC) activity and PKC translocation in response to serotonin were investigated in platelets obtained from bipolar affective disorder subjects before and during lithium treatment. Ratios of platelet membrane-bound to cytosolic PKC activities were elevated in the manic subjects. In addition, serotonin-elicited platelet PKC translocation was found to be enhanced in those subjects.